U.S. patent application number 11/833357 was filed with the patent office on 2008-02-07 for sheet conveyance device and image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Yusuke Imai, Toshifumi Itabashi, Takuma Koizumi, Ayumu Murakami, Haruhisa Oshida, Kiyoshi Oyama, Yuichi Yamamoto.
Application Number | 20080030810 11/833357 |
Document ID | / |
Family ID | 39028850 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080030810 |
Kind Code |
A1 |
Murakami; Ayumu ; et
al. |
February 7, 2008 |
SHEET CONVEYANCE DEVICE AND IMAGE FORMING APPARATUS
Abstract
A sheet conveyance device according to an aspect of the
invention includes a sheet conveyance path formed by a guide member
having a curved surface. The curved surface is curved in a sheet
conveyance direction. In the sheet conveyance device, a flexible
sheet scanner is provided along the curved surface of the guide
member, and the flexible sheet scanner has an optical sensor layer
in which photoelectric conversion devices formed by combinations of
organic transistors and organic photodiodes are continuously
arranged in a matrix shape.
Inventors: |
Murakami; Ayumu; (Abiko-shi,
JP) ; Oshida; Haruhisa; (Abiko-shi, JP) ;
Yamamoto; Yuichi; (Toride-shi, JP) ; Imai;
Yusuke; (Toride-shi, JP) ; Oyama; Kiyoshi;
(Tokyo, JP) ; Koizumi; Takuma; (Toride-shi,
JP) ; Itabashi; Toshifumi; (Toride-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
39028850 |
Appl. No.: |
11/833357 |
Filed: |
August 3, 2007 |
Current U.S.
Class: |
358/498 ;
271/111; 271/226 |
Current CPC
Class: |
B65H 2553/414 20130101;
B65H 7/14 20130101; B65H 2515/60 20130101; B65H 5/38 20130101; B65H
2511/51 20130101; B65H 2511/20 20130101; B65H 2515/60 20130101;
B65H 2511/51 20130101; B65H 2553/45 20130101; B65H 2511/20
20130101; B65H 2220/03 20130101; B65H 2220/01 20130101; B65H
2220/03 20130101; B65H 2404/6111 20130101; B65H 2220/09
20130101 |
Class at
Publication: |
358/498 ;
271/111; 271/226 |
International
Class: |
B65H 7/14 20060101
B65H007/14; B65H 9/00 20060101 B65H009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2006 |
JP |
2006-214666 |
Claims
1. A sheet conveyance device comprising; a sheet conveyance path
formed by a guide member having a curved surface, the curved
surface being curved in a sheet conveyance direction, and a
flexible sheet scanner, provided along the curved surface of the
guide member, which detects the sheet conveyed on a sheet
conveyance path, and the flexible sheet scanner has an optical
sensor layer in which photoelectric conversion devices formed by
combinations of organic transistors and organic photodiodes are
continuously arranged in a matrix shape.
2. The sheet conveyance device according to claim 1, wherein the
sheet scanner is provided in one of a guide member disposed inside
the curved sheet conveyance path and a guide member disposed
outside the curved sheet conveyance path.
3. The sheet conveyance device according to claim 1, wherein a
pressing member is provided to press the conveyed sheet against the
sheet scanner.
4. The sheet conveyance device according to claim 3, wherein a
portion facing the sheet scanner is blackened in the pressing
member.
5. The sheet conveyance device according to claim 3, wherein a
pressing surface of the pressing member for pressing the sheet
against the sheet scanner has substantially the same curved shape
as a curved surface of the facing guide member.
6. The sheet conveyance device according to claim 3, wherein the
pressing member is a rotary member having elasticity.
7. The sheet conveyance device according to claim 4, wherein the
pressing member is formed by an endless belt member tensioned by a
plurality of pressing assist members having elasticity.
8. The sheet conveyance device according to claim 3, wherein the
pressing member includes a first pressing member and a second
pressing member, the first pressing member having a pressing
surface which presses the sheet against the sheet scanner has
substantially the same curved shape as a curved surface of the
facing guide member, the second pressing member being a rotary
member having elasticity.
9. The sheet conveyance device according to claim 1, wherein a
curved surface in which the sheet scanner is provided is a concave
curved surface in the guide member.
10. An image forming apparatus comprising; a sheet conveyance path
formed by a guide member having a curved surface, the curved
surface being curved in a sheet conveyance direction, the sheet
conveyance path guiding a sheet on which an image is already formed
in an image forming portion or a sheet on which an image is formed
in the image forming portion, and a flexible sheet scanner,
provided along the curved surface of the guide member, which
detects the sheet conveyed on a sheet conveyance path, and the
flexible sheet scanner has an optical sensor layer in which
photoelectric conversion devices formed by combinations of organic
transistors and organic photodiodes are continuously arranged in a
matrix shape.
11. The image forming apparatus according to claim 10, wherein a
pressing member is provided to press the conveyed sheet against the
sheet scanner.
12. An image reading apparatus comprising; a sheet conveyance path
formed by a guide member having a curved surface, the curved
surface being curved in a sheet conveyance direction, the sheet
conveyance path guiding an original in which an image is already
read in an image reading portion or an original in which an image
is read in the image reading portion, and a flexible sheet scanner,
provided along the curved surface of the guide member, which
detects the sheet conveyed on a sheet conveyance path, and the
flexible sheet scanner has an optical sensor layer in which
photoelectric conversion devices formed by combinations of organic
transistors and organic photodiodes are continuously arranged in a
matrix shape.
13. The image reading apparatus according to claim 12, wherein a
pressing member is provided to press the conveyed sheet against the
sheet scanner.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sheet conveyance device
for conveying a sheet and an image forming apparatus provided with
the sheet conveyance device.
[0003] 2. Description of the Related Art
[0004] Recently, in the image forming apparatus such as a printer
and a copying machine, a position of the conveyed sheet is detected
with high accuracy, a position of an image recorded in the sheet is
adjusted based on the detection result, and accuracy of image
recording position is improved with respect to the sheet.
[0005] Particularly, in a sheet conveyance path, plural sensors are
arranged in a sheet conveyance direction and a sheet width
direction orthogonal to the sheet conveyance direction to
continuously measure the position of the sheet, which allows
inclination of the sheet and a sheet conveyance speed to be
detected in addition to the position of a sheet end portion (for
example, see Japanese Patent Application Laid-Open No. 6-135600).
The image recording position is adjusted with respect to the sheet
based on the detection information, and whereby the accuracy of
image recording position is improved.
[0006] However, downsizing of the image forming apparatus is
progressing recently. Particularly in the case of a tandem type
image forming apparatus in which color image can be recorded, there
is a restriction in space where each component unit is installed in
the apparatus. Therefore, most part of the sheet conveyance path
connecting the component units are formed in a curved shape. It is
difficult that the sensors for detecting the sheet position are
continuously disposed in the sheet conveyance direction in the
curved conveyance path. Therefore, the accuracy of image recording
position is hardly improved in the case of the image forming
apparatus in which most part of the conveyance paths are formed in
the curved shape.
SUMMARY OF THE INVENTION
[0007] In view of the foregoing, the present invention continuously
provides a sheet conveyance device and image forming apparatus to
detect the sheet position in the sheet conveyance direction even in
the curved sheet conveyance path to improve the accuracy of image
recording position.
[0008] In order to achieve the object, a sheet conveyance device
according to an aspect of the invention includes a sheet conveyance
path formed by a guide member having a curved surface which is
curved in a sheet conveyance direction, and a flexible sheet
scanner, provided along the curved surface of the guide member,
which detects the sheet conveyed on a sheet conveyance path, and
the flexible sheet scanner has an optical sensor layer in which
photoelectric conversion devices formed by combinations of organic
transistors and organic photodiodes are continuously arranged in a
matrix shape.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is an enlarged sectional view illustrating a sheet
scanner and a pressing member according to a first embodiment of
the invention;
[0010] FIG. 2 is an enlarged sectional view illustrating a sheet
scanner and a pressing member according to another embodiment of
the invention;
[0011] FIG. 3 is an enlarged sectional view illustrating a sheet
scanner and a pressing member according to another embodiment of
the invention;
[0012] FIG. 4 is an enlarged sectional view illustrating a sheet
scanner and a pressing member according to another embodiment of
the invention;
[0013] FIG. 5 is an enlarged sectional view illustrating a sheet
scanner and a pressing member according to another embodiment of
the invention;
[0014] FIG. 6 is a sectional view illustrating a schematic
configuration of an image forming apparatus having a curved sheet
conveyance path;
[0015] FIG. 7 is an explanatory view illustrating a sheet scanner
in which photoelectric conversion devices formed by combinations of
organic semiconductor devices are continuously arranged, FIG. 7A is
a schematic view describing a circuit configuration of the sheet
scanner, and FIG. 7B is a schematic view describing a circuit
diagram of each photoelectric conversion device.
DESCRIPTION OF THE EMBODIMENTS
[0016] Exemplary embodiments of the invention will be described in
detail below with reference to the accompanying drawings. However,
sizes, materials, and shapes of component and a relative
arrangement of components described in the following embodiments
should appropriately be changed according to a configuration and
various conditions of an apparatus to which the invention is
applied. Accordingly, the scope of the invention is not limited to
the embodiments unless particularly stated.
[0017] A schematic configuration of an image forming apparatus will
be described with reference to FIG. 6. The image forming apparatus
illustrated in FIG. 6 is an in-line type full-color image forming
apparatus in which an intermediate transfer member is used.
[0018] In the image forming apparatus of FIG. 6, a sheet is
selectively delivered from a sheet cassette 51 or a multi-sheet
tray 52 is temporally stopped at a registration roller 53.
[0019] An ITB belt 12 which is of an intermediate transfer member
is tensioned by a driving roller 81, a tension roller 82, and a
driven roller 83.
[0020] In a peripheral portion between the rollers 81 and 82 of the
ITB belt 12, four process units 13(Y), 13(M), 13(C), and 13(K)
constituting an image forming portion 11 are sequentially provided
from an upstream of a belt conveyance direction. Each process unit
13 is formed in each of color component of yellow (Y), magenta (M),
cyan (C), and black (K).
[0021] Each process unit 13 is includes a development device 14 in
which a toner having each color is stored and a photosensitive
member 15 which is of an image forming body. The process units 13
have the same structure except for the color of the storage toner.
In FIG. 6, the development device 14 and the photosensitive member
15 are shown only in the process unit 13(K), and the numerals of
the development device and photosensitive member are neglected in
other process units.
[0022] The photosensitive member 15 is rotated counterclockwise by
power from a driving source (not shown). Although the configuration
in which the photosensitive member 15 is rotated by the power from
the driving source is illustrated in FIG. 6, the invention is not
limited to the configuration of FIG. 6. For example, the
photosensitive member 15 may be rotated by following the ITB belt
12.
[0023] A charging roller 16 which is of charging unit is attached
to each photosensitive member 15 while facing the photosensitive
member 15, and the charging roller 16 imparts an even potential to
the photosensitive member 15. A cleaning device 19 which is of
cleaning unit is attached to each photosensitive member 15 while
facing the photosensitive member 15, and the cleaning device 19
recovers a residual transfer toner remaining on each photosensitive
member 15 after transfer using a blade. The charging roller 16, the
cleaning device 19, and the process unit 13 constitute an image
forming portion 11, and the charging roller 16 and the cleaning
device 19 are attached while facing the photosensitive member 15 of
each process unit. In FIG. 6, the charging roller 16 and the
cleaning device 19 are shown only in the process unit 13(K), and
the numerals of the charging roller and cleaning device are
neglected in other process units.
[0024] A laser scanner unit 17 emits a laser beam of each of the
yellow (Y), magenta (M), cyan (C), and black (K) colors to each
corresponding photosensitive member 15 according to image data to
perform image exposure.
[0025] A latent image is formed according to the image data on the
photosensitive member 15 to which the image exposure is performed
by the laser scanner 17. Then, the development device 14 develops
the latent image on each photosensitive member 15 using the toner.
The toner image on each photosensitive member 15 is sequentially
superposed on and transferred to the ITB belt 12 at the transfer
position located between ITB belt 12 and the primary transfer
roller 18. The ITB belt 12 and the primary transfer roller 18 face
each other at the transfer position. The residual transfer toner
remaining on each photosensitive member 15 after the transfer is
cleaned by each cleaning device 19 which recovers the residual
transfer toner using the blade.
[0026] At this point, the sheet which is temporally stopped at the
registration roller 53 is conveyed at the timing of the toner image
on the ITB belt 12 which is moved by the rotation of the ITB belt
12. The toner image is transferred onto the sheet by a secondary
transfer roller 54 which faces the driving roller 81 while the ITB
belt 12 is interposed therebetween. The residual transfer toner
remaining on the ITB belt 12 after the transfer is cleaned by a
cleaning device 20 which recovers the residual transfer toner using
a blade. The sheet onto which the toner image is transferred is
conveyed to a fixing device, and the fixing device 57 fixes the
toner image onto the sheet.
[0027] Then, in the case of single-sided printing, the sheet onto
which the toner image is fixed is directly discharged to a
discharge tray 59 by a discharge roller 58.
[0028] In the case of duplex printing, the sheet onto which the
toner image is fixed is conveyed to an inverting portion 71 by the
discharge roller 58, and the sheet is delivered to the registration
roller 53 again through a duplex path 72. Then, the sheet is
conveyed at the timing of the toner image formed on the ITB belt 12
in the above-described manner, and a toner image is also
transferred to a backside of the sheet by the secondary transfer
roller 54. The toner image is fixed onto the by the sheet fixing
device 57, and the sheet is discharged to the discharge tray 59
through the discharge roller 58.
[0029] A patch detection sensor (not shown) is provided on the ITB
belt 12 to detect a patch of each color. Using detection
information obtained by the patch detection sensor, the write
timing of each process unit 13 of other colors with respect to a
certain reference color is automatically adjusted such that the
shift of the toner image transfer position of each process unit 13
to the ITB belt 12 is prevented.
[0030] A sheet-shape scanner (hereinafter referred to as sheet
scanner) which is used as detection unit for detecting the sheet is
appropriately provided in the curved sheet conveyance path of the
image forming apparatus. In the sheet conveyance path of the image
forming apparatus of FIG. 6, the sheet scanners illustrated in FIG.
1 are provided in areas 91, 92, and 93 of FIG. 6.
[0031] In the curved sheet conveyance path, the areas 91, 92, and
93 where the sheet scanners are provided are illustrated only by
way of example, the area where the sheet scanner is provided is not
limited to the areas 91, 92, and 93. The area 91 indicates a
delivery area 91 located on the upstream of the registration roller
53 in the sheet conveyance direction, the area 92 indicates a
conveyance area 92 which is located on the downstream of the
registration roller 53 and on the upstream of the position where
the image is transferred to the sheet, and the area 93 indicates a
re-delivery area 93 located on the upstream of the registration
roller 53.
[0032] The sheet scanner which is of sheet detection unit will be
described with reference to FIG. 7, and a configuration in the
neighborhood of the sheet scanner in the curved sheet conveyance
path will be described with reference to FIG. 1.
[0033] Recently, there has been proposed the sheet scanner in which
an organic semiconductor device is used as a photoelectric
conversion device. The sheet scanner has an optical sensor layer in
which the photoelectric conversion devices formed by combinations
of organic transistors and organic photodiodes are continuously
arranged. For example, in the sheet scanner, a reading pixel which
is of an optical sensor is formed on a plastic film by the
combination of the organic transistor and the organic photodiode,
and the reading pixels are arranged in a matrix shape, namely, the
reading pixels are arranged in row and column directions. When the
reading pixel (optical sensor) is irradiated with light, the
organic photodiode generates electric current.
[0034] FIG. 7 illustrates a mode of the sheet scanner. FIG. 7A is a
schematic view describing a circuit configuration of the sheet
scanner in which the optical sensors formed by the organic
semiconductor devices are arranged in a matrix shape, and FIG. 7B
is a schematic view describing a circuit configuration of each
optical sensor.
[0035] Referring to FIG. 7A, reading pixels 61 arranged in one
column line are connected to word lines 63 respectively, and the
word lines 63 are connected to a column decode line 67 through
word-line selectors 70. The reading pixels 61 arranged in one row
line are connected to bit lines 64, and the bit lines 64 are
connected to a row decode line 69 through bit-line selectors 71. A
current of the predetermined reading pixel 61 is read by specifying
addresses of the column decode line 67 and row decode line 69. A
position (state) of the sheet located on the sheet scanner can be
detected by reading the current of each reading pixel 61. Referring
to FIG. 7B, each reading pixel 61 is formed by a combination of an
organic transistor 61a and an organic photodiode 61b. In this case,
the column direction is set to the sheet conveyance direction and
the row direction is set to the sheet width direction orthogonal to
the sheet conveyance direction.
[0036] The reading pixel and a peripheral circuit thereof are
formed on a base-material sheet such as a flexible plastic film,
and whereby an elastically bendable flexible sheet scanner is
formed.
[0037] Referring to FIG. 1, conveyance guides 102 and 103 which are
of the guide member for guiding the conveyed sheet, and the
conveyance guides 102 and 103 are formed in the shape curved in the
conveyance direction of the sheet P. The conveyance guides 102 and
103 constitute the curved sheet conveyance path. A sheet scanner
101 has the above configuration, the sheet scanner 101 is extremely
thin (thickness is not more than 0.5 mm), and also has elasticity
so that it may be flexibly bent. Therefore, the sheet scanner 101
can be used in the curved shape, and has extremely high usefulness.
The sheet scanner 101 is formed in the flexible manner, so that the
sheet scanner 101 can be provided in the curved shape along the
curved surface of the conveyance guide. The sheet scanner 101 is
bonded to a concave curved surface 102a of the conveyance guide 102
inside the curved sheet conveyance path using a bonding member such
as a double-side adhesive tape.
[0038] In the first embodiment, the sheet scanner has the
configuration in which the reading pixels are arranged in the
base-material sheet. However, the invention is not limited to the
first embodiment. In the sheet scanner, because the reading pixel
which is of the photoelectric conversion device is formed by the
organic semiconductor devices such as the organic transistor and
the organic photodiode, the reading pixel can directly be formed on
the conveyance guide by utilizing, e.g., a precise printing
technique. Additionally, because the number of reading-pixel lines
can arbitrarily and selectively be formed in the row or column
direction, the one-line sensor array can easily be formed in the
sheet conveyance direction. Because the reading pixels can be
formed and arranged on the conveyance guide or the base-material
sheet, even if the sheet conveyance path is curved as described
above, the reading pixels can continuously be disposed along the
conveyance path which being able to detect the sheet.
[0039] In the sheet scanner, the organic photodiode is emitted by
itself and the reflected light is read. Therefore, a particular
light source is not required in the sheet scanner 101.
[0040] In the curved conveyance path in which the sheet scanner 101
is provided, a pressing member 104 is provided to press the sheet P
against the sheet scanner 101 in order to prevent flutter of the
sheet P in the conveyance path. A biasing member 105 biases the
pressing member 104 toward the direction in which the sheet is
pressed against the sheet scanner 101.
[0041] At this point, the pressing member 104 presses the sheet P
against the sheet scanner 101 using a pressing surface 104a having
the same curved shape as the surface (curved surface 102a) of the
conveyance guide 102 to which the sheet scanner 101 is bonded.
[0042] Therefore, the sheet P is conveyed while being in close
contact with the sheet scanner 101 in both the sheet conveyance
direction and the sheet width direction orthogonal to the sheet
conveyance direction, which eliminates the generation of a reading
error caused by the conveyance of the sheet P at the position where
the sheet P is separated away from the sheet scanner 101.
[0043] The pressing surface (facing portion) 104a of the pressing
member 104 is formed by a black resin member or the pressing
surface 104a is configured such that the black resin film having a
good sliding property is bonded to a surface of a resin member.
When the sheet is not conveyed, the light emitted from the organic
photodiode is not reflected by a black region of the pressing
member 104 in the sheet scanner 101, so that a charge (current)
accumulated in the organic transistor becomes a low level.
[0044] On the other hand, when the sheet P is conveyed between the
sheet scanner 101 and the pressing member 104, the light reflected
from the sheet P is incident to the organic transistor with respect
to the light emitted from the organic photodiode, so that the
charge (current) accumulated in the organic transistor becomes a
high level.
[0045] The sheet scanner 101 can detect the presence or absence of
the sheet according to the level of the charge accumulated in the
organic transistor, and the charge accumulated in the organic
transistor depends on the presence or absence of the sheet. Because
the photoelectric conversion devices are arranged in the matrix
shape in the sheet conveyance direction and sheet width direction
on the sheet scanner 101, the presence or absence of the sheet can
continuously be detected in each of the sheet conveyance direction
and sheet width direction.
[0046] A position of a leading end, a rear end, or a side end of
the sheet in the conveyance direction, a conveyance state such as
sheet skew, and a sheet conveyance speed can be detected based on
the obtained pieces of position data in the conveyance direction
and width direction of the conveyed sheet and the time-series data
thereof. For example, the position of the latent image exposed on
the photosensitive member 15 can finely be adjusted by shifting or
rotating the position of the latent image by a predetermined amount
based on the detection information. The delivery timing performed
by the registration roller 53 is adjusted, and a speed of the
driving unit such as the registration roller 53, the secondary
transfer roller 54, and the ITB belt 12 which are involved in the
sheet conveyance speed is finely corrected. Therefore, the image
can be recorded at a proper position with a proper magnification
with respect to the sheet, and the accuracy of image recording
position is improved.
[0047] The thin sheet scanner 101 having the elasticity is disposed
in the conveyance guide 102 constituting the curved conveyance
path, which allows plural sheet position detection unit to be
continuously provided in the sheet conveyance direction and sheet
width direction with space-saving.
[0048] The pressing member 104 is provided to press the conveyed
sheet against the sheet scanner 101, which allows the detection
error to be prevented. The sheet floats from the sheet scanner 101
due to the flutter of the sheet in the curved conveyance path,
which causes the detection error.
[0049] The pressing surface 104a of the pressing member 104 is
formed in the same curved shape as the curved surface 102a of the
conveyance guide 102 provided in the sheet scanner 101, which
allows the flutter of the sheet to be further prevented.
[0050] The pressing surface 104a of the pressing member 104 facing
the sheet scanner 101 is blackened, which allows a difference of
charge (current) accumulated in the sheet scanner 101 to be
provided according to the presence or absence of the sheet to
prevent the sheet detection error of the sheet scanner 101.
[0051] The sheet scanner 101 of the conveyance guide 102 in which
the sheet scanner 101 is provided is formed in the concave shape,
which conveys the sheet more smoothly.
[0052] Other embodiments which differ from the first embodiment
will be described with reference to FIGS. 2 to 5. Other embodiments
illustrated in FIGS. 2 to 5 will be described below. FIGS. 2 to 5
are enlarged sectional views illustrating the arrangement of the
sheet scanner in the areas 91, 92, and 93 of the curved conveyance
path in the image forming apparatus of FIG. 6.
[0053] Referring to FIG. 2, conveyance guides 202 and 203 which are
of the guide member for guiding the conveyed sheet P, and the
conveyance guides 202 and 203 are formed in the shape curved in the
conveyance direction of the sheet P. The conveyance guides 202 and
203 constitute the curved sheet conveyance path. A sheet scanner
201 is a flexible sheet scanner (see FIG. 7) having the above
configuration, the sheet scanner 201 is extremely thin (thickness
is not more than 0.5 mm), and also has the elasticity so that it
may be flexibly bent. In this case, the sheet scanner 201 is bonded
to a concave curved surface 203a of the conveyance guide 203
outside the curved sheet conveyance path using a bonding member
such as a double-side adhesive tape.
[0054] In the curved conveyance path in which the sheet scanner 201
is provided, a pressing member 204 is provided to press the sheet P
against the sheet scanner 201 in order to prevent flutter of the
sheet P in the conveyance path. A biasing member 205 biases the
pressing member 204 toward the direction in which the sheet is
pressed against the sheet scanner 201.
[0055] At this point, the pressing member 204 presses the sheet P
against the sheet scanner 201 using a pressing surface 204a having
the same curved shape as the surface (curved surface 203a) of the
conveyance guide 203 to which the sheet scanner 201 is bonded.
[0056] Therefore, the sheet P is conveyed while being in close
contact with the sheet scanner 201 in both the sheet conveyance
direction and the sheet width direction orthogonal to the sheet
conveyance direction, which eliminates the generation of the
reading error caused by the conveyance of the sheet P at the
position where the sheet P is separated away from the sheet scanner
201.
[0057] Particularly, in the configuration of FIG. 2, the conveyance
guide 203 outside the conveyance path in which the sheet scanner
201 is provided receives a reaction force generated by rigidity of
the sheet conveyed in the curved sheet conveyance path. Therefore,
when compared with the configuration of FIG. 1 in which the sheet
scanner is provided in the conveyance guide inside the conveyance
pat, the flutter of the sheet can be prevented better, and the
reading error caused by the flutter of the sheet can surely be
prevented.
[0058] The pressing surface (facing portion) 204a of the pressing
member 204 is formed by the black resin member or the pressing
surface 204a is configured such that the black resin film having
the good sliding property is bonded to the surface of the resin
member. When the sheet is not conveyed, the light emitted from the
organic photodiode is not reflected by a black region of the
pressing member 204 in the sheet scanner 201, so that the charge
(current) accumulated in the organic transistor becomes the low
level.
[0059] On the other hand, when the sheet P is conveyed between the
sheet scanner 201 and the pressing member 204, the light reflected
from the sheet P is incident to the organic transistor with respect
to the light emitted from the organic photodiode, so that the
charge (current) accumulated in the organic transistor becomes the
high level.
[0060] The sheet scanner 201 can detect the presence or absence of
the sheet according to the level of the charge accumulated in the
organic transistor, and the charge accumulated in the organic
transistor depends on the presence or absence of the sheet. Because
the photoelectric conversion devices are arranged in the matrix
shape in the sheet conveyance direction and sheet width direction
on the sheet scanner 201, the presence or absence of the sheet can
continuously be detected in each of the sheet conveyance direction
and sheet width direction.
[0061] Referring to FIG. 3, conveyance guides 302 and 303 which are
of the guide member for guiding the conveyed sheet P, and the
conveyance guides 302 and 303 are formed in the shape curved in the
conveyance direction of the sheet P. The conveyance guides 302 and
303 constitute the curved sheet conveyance path. A sheet scanner
301 is a flexible sheet scanner (see FIG. 7) having the above
configuration, the sheet scanner 301 is extremely thin (thickness
is not more than 0.5 mm), and also has the elasticity so that it
may flexibly bent. In this case, the sheet scanner 301 is bonded to
the concave curved surface 303a of the conveyance guide 303 outside
the curved sheet conveyance path using a bonding member such as the
double-side adhesive tape.
[0062] In the curved conveyance path in which the sheet scanner 301
is provided, a pressing member 304 is provided to press the sheet P
against the sheet scanner 301 in order to prevent flutter of the
sheet P in the conveyance path. A biasing member 305 biases the
pressing member 304 toward the direction in which the sheet is
pressed against the sheet scanner 301.
[0063] The pressing member 304 is a rotary member formed by a foam
sponge having elasticity, and the pressing member 304 is rotated by
receiving drive from driving unit (not shown).
[0064] The pressing member 304 is elastically deformed by a biasing
force of the biasing member 305, and a nip is formed between the
pressing member 304 and the sheet scanner 301. The sheet scanner
301 detects the conveyed sheet in the nip. That is, the rotary
member 304 having the elasticity is rotated while a pressing
surface 304a having the same curved shape as the surface (curved
surface 303a) of the conveyance guide 303 to which the sheet
scanner 301 is bonded is formed by the elasticity of the rotary
member 304 and the biasing force of the biasing member 305.
[0065] Therefore, the sheet P is conveyed while being in close
contact with the sheet scanner 301 in both the sheet conveyance
direction and the sheet width direction orthogonal to the sheet
conveyance direction, which eliminates the generation of the
reading error caused by the conveyance of the sheet P at the
position where the sheet P is separated away from the sheet scanner
301.
[0066] Referring to FIG. 4, conveyance guides 402 and 403 which are
of the guide member for guiding the conveyed sheet P, and the
conveyance guides 402 and 403 are formed in the shape curved in the
conveyance direction of the sheet P. The conveyance guides 402 and
403 constitute the curved sheet conveyance path. A sheet scanner
401 is a flexible sheet scanner (see FIG. 7) having the above
configuration, the sheet scanner 401 is extremely thin (thickness
is not more than 0.5 mm), and also has the elasticity so that it
may flexibly bent. In this case, the sheet scanner 401 is bonded to
a concave curved surface 403a of the conveyance guide 403 outside
the curved sheet conveyance path using the bonding member such as
the double-side adhesive tape.
[0067] In the curved conveyance path in which the sheet scanner 401
is provided, a pressing member 404 is provided to press the sheet P
against the sheet scanner 401 in order to prevent flutter of the
sheet P in the conveyance path.
[0068] The pressing member 404 is formed by an endless belt member,
and the pressing member 404 is tensioned by pressing assist members
406a and 406b having elasticity. Biasing members 405a and 405b bias
the pressing assist members 406a and 406b toward the direction in
which the sheet is pressed against the sheet scanner 402. The
pressing member 404 is rotated by receiving the drive from driving
unit (not shown) through one of both the pressing assist members
406a and 406b.
[0069] The pressing member 404 is elastically deformed by biasing
forces of the biasing members 405a and 405b, and nips 407a and 407b
are formed between the pressing member 404 and the sheet scanner
401. That is, the belt member 404 is rotated by the biasing force
of the biasing member 305 while elastically deformed in the track
of the surface (curved surface 403a) of the facing conveyance guide
403 to which the sheet scanner 401 is bonded.
[0070] Therefore, the sheet P is conveyed while being in close
contact with the sheet scanner 401 in both the sheet conveyance
direction and the sheet width direction orthogonal to the sheet
conveyance direction, which eliminates the generation of the
reading error caused by the conveyance of the sheet P at the
position where the sheet P is separated away from the sheet scanner
401.
[0071] Referring to FIG. 5, conveyance guides 502 and 503 which are
of the guide member for guiding the conveyed sheet P, and the
conveyance guides 502 and 503 are formed in the shape curved in the
conveyance direction of the sheet P. The conveyance guides 502 and
503 constitute the curved sheet conveyance path. A sheet scanner
501 is a flexible sheet scanner (see FIG. 7) having the above
configuration, the sheet scanner 501 is extremely thin (thickness
is not more than 0.5 mm), and also has the elasticity so that it
may be flexibly bent. In this case, the sheet scanner 501 is bonded
to a concave curved surface 503a of the conveyance guide 503
outside the curved sheet conveyance path using the bonding member
such as the double-side adhesive tape.
[0072] In the curved conveyance path in which the sheet scanner 501
is provided, pressing members 504a and 504b are provided to press
the sheet P against the sheet scanner 501 in order to prevent
flutter of the sheet P in the conveyance path.
[0073] The first pressing member 504a has a pressing surface 507a
having the same curved shape as the surface (curved surface 503a)
to which the sheet scanner 501 is bonded to the conveyance guide
503, and a biasing member 505a biases the first pressing member
504a toward the direction in which the sheet P is pressed against
the sheet scanner 501. Accordingly, the pressing member 504a
presses the sheet P against the sheet scanner 501 in the pressing
surface 507a.
[0074] The second pressing member 504b is a rotary member formed by
the foam sponge having the elasticity, and the second pressing
member 504b is rotated by receiving the drive from driving unit
(not shown). The rotary member 504b is biased toward the direction
in which the sheet is pressed against the sheet scanner 501 by a
biasing member 507b.
[0075] The pressing member 504b is elastically deformed by a
biasing force of the biasing member 505b, and a nip is formed
between the pressing member 504b and the sheet scanner 501. The
sheet scanner 501 detects the conveyed sheet in the nip. That is,
the rotary member 504b having the elasticity is rotated while a
pressing surface 504b having the same curved shape as the surface
(curved surface 503a) of the conveyance guide 503 to which the
sheet scanner 501 is bonded is formed by the elasticity of the
rotary member 504b and the biasing force of the biasing member
505b.
[0076] Therefore, the sheet P is conveyed while being in close
contact with the sheet scanner 501 in both the sheet conveyance
direction and the sheet width direction orthogonal to the sheet
conveyance direction, which eliminates the generation of the
reading error caused by the conveyance of the sheet P at the
position where the sheet P is separated away from the sheet scanner
501.
[0077] In the embodiments of FIGS. 1 to 5, the curved surface to
which the sheet scanner is bonded is formed in a C-shape. However,
the invention is not limited to a C-shape. For example, the
invention can be applied to curved surfaces having different shapes
such as an S-shape.
[0078] Although the printer is illustrated as the image forming
apparatus in the above embodiments, the invention is not limited to
the printer. Examples of the image forming apparatus include a
scanner, a copying machine, a facsimile, and a multifunction
peripheral in which these functions are combined. The same effects
can be obtained by applying the invention to the sheet conveyance
device used in these pieces of image forming apparatus.
[0079] Although the sheet conveyance device is integral with the
image forming apparatus in the above embodiment, the invention is
not limited to the above embodiments. For example, the sheet
conveyance device may be detachably attachable to the image forming
apparatus, and the same effect can be obtained by applying the
invention to the sheet conveyance device.
[0080] Although the sheet conveyance device for conveying the sheet
such as the recording paper of the recording target is illustrated
in the above embodiments, the invention is not limited to the above
embodiments. For example, the same effects can be obtained by
applying the invention to the sheet conveyance device for conveying
the sheet such as the original of the read target to the image
forming apparatus.
[0081] This application claims the benefit of priority from the
prior Japanese Patent Application No. 2006-214666 filed on Aug. 7,
2006 the entire contents of which are incorporated by reference
herein.
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